Method of block recording data on a magnetic tape

ABSTRACT

A METHOD OF BLOCK RECORDING DATA ON A MAGNETIC TAPE COMPRISES (1) FEEDING DATA AT A SELECTED FIRST RATE TO A STORAGE UNIT UNTIL THERE HAS BEEN STORED A SELECTED AMOUNT LESS THAN DATA CONTAINED IN ONE BLOCK AND (2) FEEDING THE STORED DATA TO A RECORDING UNIT HAVING A TAPE TRANSPORT AT A SECOND SELECTED RATE WHICH IS FASTER THAN THE FIRST RATE WHILE CONTINUING TO FEED DATA TO THE STORAGE UNIT. THE RATES OF STORAGE AND RECORDING ARE SELECTED SO THAT THE DATA STORED IN THE STORAGE UNIT ARE EXHAUSTED SIMULTANEOUSLY WITH COMPLETION OF RECORDING OF ONE BLOCK OF DATA BY THE RECORDING UNIT. THE TAPE TRANSPORT OPERATES AT A CONTANT SPEED DURING BOTH PERIODS, THE LENGTH OF THE INTERRECORD GAP BETWEEN SUCCESSIVE BLOCKS BEING DETERMINED BY THE SELECTED STORAGE AND RECORDING RATES.

United States Patent nu 3,588,840

[72] Inventors Takuyl Nomura [56] References Cited (232:), Knmthoya, Hoya-Machi Kitatama- UNITED STATES PATENTS 2,913,707 11/1959 Goldberget al...... 340/174 7 g gf fg fifi 3,293.6!3 l2/1966 Gabor .v 340/1725 A I No 796 704 3.333,247 7/1967 Hadley r, 340/1725 [22] 52 rebs 1969 3,346,849 10/1967 Jones et all .1 340/1725 Patemed 1971 3,444,541 5/1969 Irwin IMO/174.1 Priority Dec 2 3,454,930 7/1969 Schoeneman 340/1725 w' 3,482,230 12/1969 Girling IMO/174.1 [31 645l 1/63 Primary Examiner- Paul J. Henon Continultiolrln-pu-t of application Ser. No. 413,583, Nov. 24. 1964, now abandoned.

METHOD OF BLOCK RECORDING DATA ON A MAGNETIC TAPE 4 Claims, 6 Drawing Figs.

lnt.Cl Gl1b5/00, G06f 3/00 Field of Search 340/1741 Assistant Examiner-R. F. Chapuran Attorneys-Robert E. Burns and Emmanuel Jr Lobato ABSTRACT: A method of block recording data on a magnetic tape comprises (1) feeding data at a selected first rate to a storage unit until there has been stored a selected amount less than data contained in one block and (2) feeding the stored data to a recording unit having a tape transport at a second selected rate which is faster than the first rate while continuing to feed data to the storage unit. The rates of storage and recording are selected so that the data stored in the storage unit are exhausted simultaneously with completion of recording of one block of data by the recording unit. The tape trans port operates at a constant speed during both periods, the length of the interrecord gap between successive blocks being determined by the selected storage and recording rates.

ANDb All/D HiAD'l STORAGE gal/:2 g

4 UN! T H:

AMP- 7 HEAD7 ADDRESS-I TAPE RECORDER .SWP STAR! PATENTEDJUNZBIBH 3.588.840

SHEET 1 BF 4 I l I A B A 8 FIG.

r STORAGE UNIT -3b Data Input Rate 30 I A! Rcne f SM SW2 2 3 C L STORAGE UNIT 2 w REZSSEER FIG. 2

55 Data Input STORAGE Rate 50 At Rate f UNIT f 5c 6-- CLOCK CIRCljIT TAPE J RECORDER PATENIED JUN28 19m SHEET 3 OF 4 PATENTEH JUN28 I971 SHEET M 0F 4 FIG. 6

FF, 7 F

ADDRESS cou-1ER-2 (out nut) V DQIU. 7 F

METHOD OF BLOCK RIXIORDING DATA ON A MAGNETIC TAPE This application is a continuation-in-part of our application Ser. No. 413.583 now abandoned filed Nov. 24, I964 which claims priority of our earlier Japanese application 645N163 filed Dec. 2. l963.

The present invention relates to a method for recording data of digital signals on magnetic tape for use in apparatus such as electronic computers. etc.

The recording of data on magnetic tape in computers or data processing systems, etc. is usually effected by a method providing a format of block recording. By this method. sequential groups or blocks of data are recorded on magnetic tape, providing a constant interval between blocks of recorded data. These intervals are referred to as interrecord gaps. According to the conventional block recording method, two storage units comprising socalled magnetic cores are used. The conventional block recording method is not economical by the reason of the necessity of using two units of magnetic cores. each having a storage capacity corresponding to the number of data being recorded in one block on the magnetic tape. Therefore. the method has the disadvantage that the size of the magnetic core storage must be increased with an increase of the number of data being recorded in one block on the magnetic tape.

The principal object of the invention is to provide an improved method of block recording of data incoming at an almost constant rate. using a single storage unit and a recording unit comprising recording means and tape transport means.

Another object of the invention is to provide a method of block recording using a tape transport means which moves the magnetic tape at a constant speed.

Still another object of the invention is to provide a method of block recording using a single storage unit having a capacity equivalent to or greater than the number of the input data during the motion of the tape over the length of an interrecord gap but less than the number of data to be recorded in one block.

A further object of the invention is to provide a method of block recording capable of selecting a bloclt sire and a length of interrecord gap from several different values in a specific system.

Since the features of the invention are provided by using a much smaller storage capacity than heretofore required, it is possible to reduce the cost and size of the system.

The invention will be better understood from the following description taken in connection with the accompanying drawings in which:

H6. 1 is a diagram to explain a format of block recording on a magnetic tape;

FIG. 2 is a schematic diagram illustrating a prior art method for block recording;

FIG. 3 is a schematic diagram illustrating the method for block recording according to an embodiment of the invention;

FIG. 4 is a block diagram illustrating the method for block recording according to another embodiment of the invention;

FIG. 5 is a time chart showing control pulses employed in the embodiment of FIG. 4; and

FIG. 6 is a time chart showing the operation of each part of the system illustrated in H0. 4.

Before explaining the embodiment of tee invention shown in FIG. 3. it is helpful to explain the conventional system. to clarify the features of the present invention.

As illustrated in FIG. l. the hatched portions A of a magnetic tape indicate recorded portions. each of which is herein called a "block" and other portions B which are blank indicate nonrecorded portions that are herein called "interrecord gaps. sometimes abbreviated as "16. on the tape. The number of bits being recorded in one block is In the conventional method of block recording shown in FIG. 2. there are provided two storage units 1 and 2. each comprising magnetic cores. and a magnetic tape recording unit 3. The storage capacity of each storage unit has a value corresponding to the number of bits to be recorded in one block on the tape. The number of bits being recorded in one block is herein designated as N bits. The magnetic recording unit 3 comprising recording means 30 and a tape transport means 3b records the data of digital signals on a magnetic tape 3c.

By means of a double throw switch SW1, the data to be recorded is fed alternatively to the storage unit l. or to the storage unit 2. A double throw switch Sw, feeds the data stored respectively in the storage unit 2 or 1 to the recording unit 3.

The manner of operation of the switches Sw, and Sw, is as follows: in a first stage. the switch Sw, connects the input terminal l to the storage unit I. and the switch Sw, connects the storage unit 2 to the recording unit 3. so that the data of electrical signals are fed to the storage unit I at a rate 1'. corresponding to the incoming data. After the storage unit 1 has stored the data of N bits which correspond to its storage capacity. the connections of the switches Sw. and Sw, are simultaneously reversed. Data is then fed continuously to the storage unit 2 in the same manner at a rate I, and. at the same time. the data that has been stored in the storage unit 1 begins to be recorded on the magnetic tape in the recording unit 3 at a rate 1;. After N bits of data have been fed to the storage unit 2, the connections of the switches Sw. and Sw are again reversed and the foregoing operation is repeated. By keeping the relation f f,' and by repeating the above-mentioned operation, a recorded magnetic tape in a format of block recording as shown in FIG. I is obtained. ln this case. the time T required to feed the data of N bits to the storage unit 1 or 2 and the time T, required to record the data of N bits on the magnetic tape by the recording unit 3 are given by Now, sincef.' T, T,, and

AT-T.T, 0 with T,==T,AT, with the tape fed continuously at a constant speed by the tape transport. AT is the time corresponding to the motion of the tape over the length of an interrecord gap. In this case. N bits of data are recorded in one block.

In the foregoing case. the magnetic tape in the recording unit 3 is fed continuously at a constant speed and does not stop when the switches Sw, and Sw, are switched over. As above mentioned, the conventional block recording method requires two storage units. each of which has a storage capacity corresponding to the number of data being recorded in one block. Therefore the size of the storage unit must be enlarged if it is desired to increase the number of data to be recorded in one block. Thus. the conventional method of block recording is uneconomical.

FIG. 3 shows an embodiment of the invention providing a single storage unit 4 to store the data from an input tenninal l. the capacity of the unit being M bits. a magnetic tape recording unit 5 comprising tape transport means 5!; with a constant tape speed and recording means 50 to record the data on a magnetic tape 5c. and a switch Sw to feed the storage output of the storage unit 4 into the recording unit 5. Although the switch Sw could be controlled manually. It is shown as being operated under control of a clock circuit 6.

With this apparatus. the method of the invention is performed by the following manner: In the first stage. the data are fed to and stored in the storage unit 4 at a rate f. correspond ing to the rate of the incoming data while switch Sw is kept in an open or "off condition so that no data is recorded although the tape is being moved at constant speed by the tape transport. Then. just after storing the data of M bits. the switch 8w is changed to closed or on" condition instantaneously and the data that has been stored in the storage unit 4 begins to be recorded on the magnetic tape 5c by the recording unit 5 at a rate F,. while the storing operation of the storage unit 4 is still continued.

ln this case, if f. f,, that is. the recording rate is faster than that of storing, the data stored in the storage unit 4 are gradually exhausted after a definite time. The switch Sw is then changed to "ofF condition simultaneously when the data stored in the storage unit are completely exhausted, and hence the recording operation of the recording unit 5 is stopped while the tape continues to be moved at constant speed by the tape transport means 5b. This condition is continued until the number of data stored in the storage unit 4 becomes M bits Then, the switch Sw is again changed to on condition to record the data on the magnetic tape just after the number of data stored in the storage unit 4 becomes M bits.

By repetition of the foregoing cycle of operation, the data is recorded on the magnetic tape in a format of block recording. The time AT corresponding to the interrecord gap is AT =M/f, since AT is the time required for storing M bits of data in the storage unit 4. The recording time of one block T and the number of data N being recorded in one block are determined by the following formulas,

It is clear that in the process of the present invention, it is possible to select the length of the interrecord gap and the number of data being recorded in one block in suitable condi tions by appropriately selecting the ratio of the rates fJf and M. It is sufficient to use a storage unit with a much smaller capacity compared with those of the conventional block recording system to obtain better results.

The apparatus illustrated in FIG. 4 comprises a magnetic core-type storage unit and a tape recorder 11. The storage unit 10 is capable of storing seven bits of information simultaneously (six signal bits and one parity bit) and accordingly has seven data input channels. The tape recorder is likewise capable of recording seven hits of information simultaneously on a tape llc driven by a tape transport 11b and accordingly has seven recording heads designated HEAD-lHEAD-7 connected respectively to the output side of the storage unit 10 through amplifiers designated AMP-l-AMP-7.

The write" and read functions of the storage unit 10, and hence the recording of data by the tape recorder 11 are controlled by a control system comprising a main oscillator 12 having two outputs supplying respectively clock pulses f0 and fa which are of the same frequency but 180 out of phase with one another as illustrated in FIG. 5. The clock pulsesfo are fed to FREQUENCY DIVIDER 1 having a division factor X to yield clock pulses f, which are fed through a switch or gate AND, to ADDRESS COUNTER-l and ADDRESSl controlling the wrile" function of the storage unit 10. The clock pulses {0' are fed to FREQUENCY DIVIDER 2 having a division factor y to yield clock pulses f, which are fed through switches or gates AND, and AND, to ADDRESS COUNTER 2 and ADDRESS 2 and also to the "read" line R of the storage unit 10 to control the read function of the storage unit and hence the recording function of the tape recorder 11. The division factor x of FREQUENCY Dl'VIDER l is lower than the division factor y of FREQUENCY DIVIDER 2, giving the relationships f -'/y =fa/y (sincefo'=fo) selecting it and y as fi z when gate AND, and data input gates AND to AND are closed, input data are stored in the magnetic cores of the storage unit 10 at the ratef, in synchronism with the clock pulses f,; when gates AND, and AND are closed, output data read from the magnetic cores of the storage unit 10 are recorded on the magnetic tape of the tape recorder 11 at the ratef, in synchronism with the clock pulses f, The relationship of the clock pulses is illustrated in FIG. 5.

Gates AND, AND, and AND, to AND, are controlled by a startstop flip-flop FF 1. Switch AND which corresponds to switch Sw in the embodiment of FIG. 3, is controlled by a flipflop FFZ in response to pulses c received from ADDRESS COUNTER-l and pulses (9 received from COUNTER-3 which is actuated by pulses a received from ADDRESS COUNTER-2 as will be explained more fully below.

The method of the present invention will now be explained with reference to the apparatus shown in FIG. 4, assuming the division factors of the frequency dividers to be i=4 and y=3 whereby f,=/4 and f,=fo'l3 =fo/3 as illustrated in FIG. 5. The time relationship of the several functions is illustrated in FIG. 6. When a start signal enters the flip-flop FF! and sets it, the AND gates AND,,, AND, and AND, are actuated to cause the write clock pulse f, to enter the ADDRESS COUNTER-l through the AND gate AND,,, and the output determines the address of the magnetic cores of the storage unit to store the input data for each write pulse of f, by means of the address logic ADDRESS-l. Data are thus stored in the storage unit if] at the rate f At this time, as the flip-flop (FF,) for actuating the switch AND is in reset condition, the switch AND is kept in an open or off" condition, so that the data stored in the magnetic cores are not read.

Since the storage operation of the input data into the core storage is made at the rate 1",, starting from the core element of the first address (No. l for example) and ending at the element of the last address (No. M for example), the whole storage unit 10 is filled up with N-data in a time T, after the beginning of the storage operation: T ,=N If.

At the moment when the whole storage unit 10 is filled up, that is, corresponding to the storing of a datum into the last storage element of the address number M, or corresponding to the transition of the condition of the ADDRESS COUNTER-l from the count number M to l, a control pulse 0 is generated by the ADDRESS COUNTER-I. This is shown by the references ADDRESS COUNTER-l" and c in the time chart (FIG. 6). This pulse signal c enters the set" input of the flip-flop FFZ and turns the flip-flop FFZ to a set condition to actuate the gate AND to turn it to a closed or on condition. Therefore, the "read clock pulses}; enter the AD- DRESS COUNTER-2 and the read line R of the core storage unit 10. The data stored in the magnetic cores by the abovementioned process are thereupon read and are fed through AMPLIFIERS l7 to the recording HEADS l7 of the tape recorder 11. This situation corresponds to the time t 1 indicated on the reference lines ADDRESS COUNTER-2" and din the time chart (FIG. 6). The tape transport 1 lb of the tape recorder starts at the beginning of operation, being con trolled, for example, by flip-flop FFl and continues to run at constant speed.

Starting from the first address (No. l) of the storage element, the read" operation is made at the rate f, and the address of the storage element, from which a datum is read, is determined by the ADDRESS COUNTER-2, with the aid of the address logic ADDRESS-2 arriving at the last address (No. M) in a time T, after the beginning of the read operation, where T N/f,

In this period, the "write" operation is still being continued at the rate I, and at the end of this period T, the address of the storage unit, in which a datum is written, is

At this moment, that is, corresponding to the reading of a datum from the last address M and the transition of the condition of the ADDRESS COUNTER-2 from the count number M to 1, a shift pulse a is generated by the ADDRESS COUNTER-2. This situation corresponds to the time t of the time chart (FIG. 6).

The shift pulse a enters and steps the repetition counter COUNTER3. While the write and read operations are con tinued by the ADDRESS COUNTERS-l and 2, an a pulse is generated by the ADDRESS COUNTER-2 at the each end of the read cycles of the storage unit when. after the repetition of K cycles. the corresponding write address is Each of the a pulses steps the repetition COUNTER-3 which also generates shift pulse b corresponding to the transition of the condition from the count number K to l. In the example illustrated in H6. 6. K=4. The number of data N recorded in one block on a tape is: N'=4M bits.

The b pulse enters the reset input of the flip-flop (FR). turning it to the reset condition and the switch AND to the open or oft condition. thereby interrupting the rea operation, while the "write operation is continued. This situation corresponds to the time r in the time chart FIG. 6. It will be seen that at time t the conditions of the components of the apparatus are the same as at the starting time 1,. The number of data stored at any instant in the storage unit 10 is indicated by the line 10 in FIG. 6. increasing to a maximum at time 1,, and then decreasing to zero by time 1 The operation which has been described is then repeated. It will be seen that between time t and 1,. data continuous to be stored while the read operation is interrupted. As the tape transport llb continues to run at constant speed. there is formed an interrecord gap lRG. At time I a pulse c from AD- DRESS COUNTER again actuates flip-flop FFZ to close switch AND and start recording of the next block on the tape.

In the operation described. the write clock pulse f, and the read clock pulse f, of magnetic cores have the relations:

Accordingly, the data begins to be stored in the magnetic cores at the time t and when the storing operation has been continued until the time 1., that is, after the lapse of time T the whole of the cores are filled up with the data. At this moment, that is. at the time t,, the "rea operation from the cores begins, and after the lapse of time from r, to t that is when the time T, has passed, one-fourth of the storage unit becomes empty; at the time 1,, that is when the time 2T, has passed after the time r,, one-half of the storage unit becomes empty. at the time t", that is when the time 3T, has passed after the time r,, three-fourths of the storage unit becomes empty; and at the time t,, that is, when the time 4T, has passed after the time t h the whole storage unit becomes empty. This is shown by the reference line 10 in FIG. 6.

By this time, the reading of the data stored in the core of the first address (No. l to the core of the last address (No. N) has been repeated four times (of course, the storing of the data in the core has also been repeated four times), so four pulse signals a have come out of the ADDRESS COUNTER-2 and entered the COUNTERJ. and one pulse signal b has come out of the COUNTER-3 and entered the reset input of the flip-flop FF thus making the flip-flop FF, turn the switch AND to the open or "off" condition. Therefore, the read clock pulses f, cease to enter the ADDRESS COUNTER-2 and the read line R of the storage unit 10. and the read operation from the magnetic cores stops. By the operations up to this stage, a number KN of the input data is recorded as one block on the magnetic tape. The time t, to 1, during which the "read" operation is stopped gives an interrecord gap IRG, since the magnetic tape is being continuously moved by the tape transport during the time in which the read" operation is interrupted. During all this time the data continue to be stored in the magnetic cores of the storage unit 10.

The described cycle of operation is repeated to record the next block of data on the tape. and so on.

From the foregoing description it will be clear that the storage capacity of the storage unit required for the method of this invention is only one-fourth of the capacity of one block and. therefore. is one-eighth of the capacity of the storage unit used in the conventional method. It is, of course, to be noted that the ratio of the capacity of the storage unit to the capacity of one block of tape can optionally be selected by changing the rates f and 1;. Thus, the storage capacity of the storage unit according to the method of this invention is far smaller than that required in the conventional method.

The present method for block recording has remarkable usefulness in the fields of computer and data processing arts, etc.

It will be understood that the invention is not limited to the use of storing units with magnetic cores or to other specific characteristics of the equipment to which reference is herein made by way of example.

It is intended. therefore, that all matter contained in the foregoing description and in the drawings shall be interpreted as illustrative only and not as limitative of the invention.

We claim:

1. A method of block recording data on a magnetic tape by means of a single storage unit and a recording unit comprising recording means and tape transport means, which comprises the steps of storing M bits of data in said storage unit at a rate f, while said tape is being moved by said transport means but no data is being recorded. thereupon feeding stored data from said storage unit to said recording unit and recording said data on the tape at a selected rate f, which is greater than I. and is less than Mf while said tape is continuously moved by said transport means and while continuing to store data in said storage unit at a rate f continuously performing said recording step at a rate f, until all of the stored data have been recorded. thereby providing a block of data which has a number of information bits greater than M and is recorded on said tape, interrupting the recording of data on the tape while continuing the storing of data in said storage unit at a rate f until M bits of data have again been stored and while continuing the transport of said tape to provide an interrecord gap. thereupon again recording the stored data on the tape to provide a succeeding block of data recorded on said tape, and repeating the foregoing cycle of operation to form on said tape successive blocks of data separated by interrecord gaps.

2. A method of recording data on a magnetic tape according to claim 1 comprising the additional step of selecting M so that the number of bits of data recorded in each block on said tape is an integral multiple greater than 1 of the number of M bits.

3. A method of block recording according to claim 1, comprising the additional step of selecting f f and M so that said interrecord gap has a length equivalent to the positions required for the recording of M bits.

4. A method of block recording data on a magnetic tape by means of a single storage unit having a plurality of storage positions, and a recording unit including recording means and tape transport means, which comprises the steps of storing M bits of first data in M positions of said storage unit at a rate f,; thereupon feeding said stored first data from said storage unit to said recording unit and recording said data on the tape at a selected rate f, which is greater than f storing additional data in said storage unit at said rate f, while continuing the recording of said stored first data on the tape at said rate f,. said additional data being stored in said M positions which have been already read into said tape. 

